How To Cut Uneven Outer Cylindrical Surface

How to cut uneven outer cylindrical surface workpiece on CNC Turning Machine? In fact, machining uneven outer cylindrical surface workpiece or irregular outer cylindrical surface workpiece on CNC turning machine center or CNC lathe machine requires a fundamental understanding of the relationships between workpiece surface integrity, tool life, type of workpiece material, size of workpiece, type of tool tip and machining parameters setting such as depth of cut, spindle speed and cutting tool feed rate and how severe the workpiece outer surface condition. Of course, the tool tip material also need to be considered but I'm not going to emphasize it here because I'm using the standard tool tip, High Speed Steel (HSS) tool tip with nose radius range from 0.4 mm to 0.8 mm to perform the tuning and facing operations. In some cases, I will use the same tool tip for turning and facing operations.



If the machining operation involve time consuming especially when performing mass production then you need to have more powerful tool tip such as carbide tool tip. In CNC turning machine center, single point cutting tool or tool tip also known as an insert because we need to insert the tool tip onto the forged tool holder and attach the tool holder on the turret system or Auto Tool Changer (ATC) before we can use it in the machining operation.



Machining the uneven outer cylindrical surface workpiece on CNC lathe machine, a rough cut need to perform. When performing rough cut on the uneven outer cylindrical surface or irregular outer cylindrical surface workpiece, it is very crucial to have a correct machining parameters setting. Incorrect machining parameters setting especially the spindle speed, feed rate and depth of cut will led to tool tip blunt very fast, crack or breakdown.





Here are my machining parameters setting when performing a turning rough cut on irregular outer cylindrical surface or uneven outer cylindrical surface workpiece. I am using CNC turning machine center with Centroid CNC Controller.

Tool = High Speed Steel (HSS) tool tip
Workpiece Material = Mild Steel SS41
Workpiece Diameter = 143 mm
Workpiece Length = 160 mm
Feed Rate = 5 F/M (Feed per Minute)
Spindle Speed = 200 RPM (Rotation per Minute)
Depth of Cut = 1 mm (total unused material remove from workpiece is 2 mm out of total diameter in 1 cycle of turning operation)

Finish cut parameters setting for turning operation

Feed Rate = 70 F/M
Spindle Speed = 800 RPM
Depth of Cut = 0.2 mm (total unused material remove from workpiece is 0.4 mm out of total diameter in 1 cycle of turning operation)





Video clip showing the turning process to cut and machining the uneven or irregular outer cylindrical surface workpiece on CNC Turning Machine Center.

CNC Lathe Boring Bar

CNC lathe boring bar is on of the CNC turning machine center tool used to enlarge the inner diameter of the pre-existing hole on the rotationally-symmetrical workpiece or cylindrical workpiece. CNC lathe boring bar consists of a long bar and an insert or a single-point cutting tool which will be positioned at the end of the long bar and use in the boring operations. Boring bar is needed especially to get an accuarate large diameter and high surface roughness in the inner surface of the cylindrical workpiece.


Boring bar



Insert or single-point cutting tool attached on the long bar and the combination of both known as boring bar



Boring operation using boring bar tool performed on the CNC turning machine center


Before the boring bar can be used in the boring operation on the cylindrical workpiece, a small hole need to drill on the center diameter of the workpice and the hole diameter must be sufficient enough to accommodate the boring bar or the boring tool. For high surface roughness, I myself use roughing cut, boring tool feed rate range from 2 to 4 feed per minute, spindle speed equal to 180 RPM and depth of cut equal to 2.5 mm. For finishing, the boring tool feed rate equal to 5 or 6 feed per minute, spindle speed is 400 RPM and depth of cut is 0.5 mm. The workpiece material is mild steel SS41

Summary for boring bar cutting operation:

Boring Bar Roughing Cut

Feed Rate = 2 ~ 4 F/M (Feed Per Minute)
Spindle Speed = 180 RPM ( Rotation Per Minute)
Depth of Cut = 2.5 mm (millimeter)

Boring Bar Finishing Cut

Feed Rate = 5 ~ 6 F/M
Spindle Speed = 400 RPM
Depth of Cut = 0.5 mm



Completed machining part. Other machining methods involved to complete this part are turning, facing and drilling



Cylindrical workpiece mild steel SS41 with high surface roughness

Video clip boring operation performed on cylindrical workpiece using CNC lathe machine center or CNC turning machine center